A preconditioner is an apparatus widely used in combination with an extruder or feed pellet mill to manufacture food products, such as, for example, flakes or pellets for cereals and snacks, pet food, pet treats, and fish feed. A preconditioner heats, hydrates, and mixes the dry raw materials (e.g., protein, fat, starch, etc.) before extrusion or milling and automatically doses the pre-treated product into the processing apparatus, e.g., extruder or feed pellet mill. A preconditioner can also be used to partially cook the starting ingredients prior to extrusion. For example, starting ingredients typically have a relatively high percentage of powdered or ground ingredients, e.g., flour-like material such as corn or wheat, that require blending with water and/or treatment with steam in the preconditioner to facilitate downstream extrusion or milling. The use of a preconditioner is advantageous in preparing products comprised of farinaceous material, such as pet food or treats, containing a relatively large percentage of flour and other ground ingredients.
Generally, a preconditioner includes injection ports for introducing steam and/or water into the chamber of the preconditioner to be mixed with other starting ingredients with mixing paddles, counter-rotating screws, or other mixing devices during processing in the preconditioner. The steam may be pressurized to about 30-80 psi prior to injection into the preconditioner. The combination of energy (thermal and mechanical) in the preconditioner can be used to partially cook ingredients and even to pregelatinize starch in the preconditioner.
The pressurized steam must condense in the preconditioner to be effective. Typically, a portion of the pressurized steam exits the preconditioner as “blow out” through a vent that exhausts a gaseous mixture to prevent the buildup of undesired pressure in the preconditioner. The gaseous mixture can include steam, air, and particulate matter comprising the starting ingredients that become aerosolized by and with the steam.
The manufacturing operations for pet and human food includes blending of raw material (dry and wet) prior to heat treatment. In general, most food formulations include grains, e.g., corn, wheat, and their products such as gluten. Some of these ingredients may be contaminated with or contain naturally-occurring pathogens, bacteria, toxins and/or mold that are known to cause illnesses. For example, meat meal and animal proteins can be contaminated with Salmonella, Staphylococcus, and Coliform bacteria such as E. coli. Cereal grains (corn, wheat, and their products), legumes (peanuts), and oilseeds may be contaminated with fungi or molds that product toxins, such as aflatoxin produced by Aspergillus. 
One function of an extruder is to quickly cook and pasteurize the food or feed at temperatures high enough to kill a majority of the microbes and destroy toxins present in the starting ingredients. Preconditioning the starting ingredients can start the kill process for microbes and/or destroy toxins. However, the introduction of pressured steam and/or water into the wet and dry starting ingredients can create blow off in the form of preconditioner exhaust. This exhaust can contain contaminated starting materials and dust that are hosts for pathogens that can survive for up to 300 days. This exhaust is typically not exposed to a high temperature kill step to destroy toxins or to kill microorganisms.
The handling of the preconditioner exhaust is a problem throughout the pet and human food processing industry. If the exhaust is untreated, which has been a common approach in the industry, then it will be dispersed throughout the production facility and settle on and coat the surfaces of the production machines, pipes, floor and other exposed surfaces in the facility. The commingling of steam with proteinaceous particulate matter and other starting ingredients provides ideal conditions to support microbial growth as those microbe(s) and their by-products are exhausted with the steam into the processing facility and deposits on surfaces. The moisture creates conditions that promote the growth of microbes that are dispersed with the exhaust, as well as other microbes, such as fungus, mold, or bacteria, that are present in the processing environment. Any toxins, e.g., aflatoxin, that may be present in the starting ingredients may also be aerosolized by the exhaust and disbursed throughout the processing environment.
The spread of microbes and toxins by the exhaust poses a food safety concern because the finished product, which is produced in the processing environment, can become contaminated through exposure to the microbes and/or toxins.
Other concerns include workplace safety. Plant operators can become ill through exposure to microbes and/or toxins exhausted into the processing environment. Additionally, the moist coating is slippery and creates a hazardous work environment that must be constantly maintained in order to avoid workplace injury. Finally, the moist coating can also cause corrosion of the processing machines and other surfaces.
Management systems for preconditioner exhaust have been developed for processing or collecting vent exhaust. These systems include collection bags, fan suction with centrifugal separators, cooling systems combined with increased diameter vent pipes, confined space such as a closed-off room to collect exhaust, and water scrubbers. All of these systems have significant limitations for a variety of reasons that include high cost or ineffective or inefficient systems. For example, baghouse collectors have been used unsuccessfully with vent stacks to filter particulate matter from the steam using a fabric filter. The particulate matter and steam form a mud-like material that clogs the filter and renders the collector ineffective for managing vent exhaust.
An alternative system implementing wet centrifugal collectors (RotoClone) centrifugally separates the exhaust into water and particulate matter and then separately collects the water and particulate matter. This type of collector introduces exhaust into a chamber having a fan or impeller that separates the exhaust into water disposed of with a drain and particulate matter disposed of in a separate chute. This collector system is inefficient because the disposal drain and chute routinely clog and require constant maintenance to prevent back up of the collector.
A further approach to managing vent exhaust uses a cooling system that operates as a condenser with a large-diameter pipe vent. When the steam cools, water along with particulate matter condenses onto the vent pipes and then drains back into the preconditioner. This system fails to treat all of the exhaust because a significant amount of steam with particulate matter does not condense and vents into the processing machinery environment. This system also requires additional utilities to operate and support the cooling system.
Another solution vents exhaust directly into a confined space such as a room. This produces similar problems as direct venting exhaust into a production facility.
Water scrubbers have been explored as a possible alternative solution for managing vent exhaust. In one type of water scrubber, water nozzles spray water into the exhaust flowing in the vent to disrupt the flow of steam and particulate matter. This causes water and particulate matter to collect in the vent pipe and then return to the preconditioner and alter the composition of the preconditioned material. Water scrubbers also require additional utilities to manage water flow to the scrubber.
Outside the field of food processing equipment, other systems have been used to remove ultra-fine particles and water droplets present in a gas stream flowing in an industrial process. For example, some centrifugal collectors use cyclonic action to separate dust particles or water droplets from the gas stream. In a typical cyclone, the dust gas stream enters a funnel-like, cyclonic container at an angle and is spun rapidly. The centrifugal force created by the circular flow directs the dust particles toward the wall of the cyclone. After striking the wall, these particles fall into a hopper located underneath the collector. The most common types of centrifugal collectors in use today are: single-cyclone separators, multiple-cyclone separators, and secondary-air-flow separators. These systems are used for removing ultra-fine particulate matter from dry gas streams.
Impact separators are another type of system used to remove ultra-fine particles and water droplets present in a gas stream flowing in an industrial process. Impact separators use fixed plates or L-shaped or U-shaped bends in tubing that causes the conveying gas stream to make a sudden change of direction. Particles and water droplets do not follow the gas stream because either inertia carries them into a surface of the separator or the gas stream becomes turbulent and slows in a dead air space. In either case, the particles and/or water fall out of the flowing gas stream. Impact separators are typically used as precleaners for industrial operations and are intended for use in removing ultra-fine, but not course, particulate matter from dry gas streams. Impact separators remove particles with high inertia or low drag from the gas stream, but low inertia or high drag particles remain in the gas stream line and continue to flow with the gas which must be passed through a filter(s). This system would not work effectively with a water saturated exhaust vented from a food processing operation.
The subject matter disclosed herein provides a particle separator apparatus, and methods of use thereof, that: (1) cleans exhaust steam or gas by removing at least 80% or more particulate matter flowing in the exhaust; (2) is a low cost alternative to more expensive vent management systems; (3) is easy to clean and does not clog readily during day-to-day use; (4) provides an easy fit with existing vent stacks used with food processing equipment; (5) reduces sanitation costs by significantly reducing, if not eliminating, the settlement of blow off on surfaces in the process operation environment, and potential contamination by microbes and their by-products (e.g., toxins) by removing uncooked meat particulates and other ingredients, as well as microbes and their by-products (e.g., toxins) from the exhaust; (6) reduces workplace hazards by significantly reducing or eliminating blow off of wet exhaust into the processing operation environment; (7) reduces the corrosion of processing equipment, e.g., extruders, pipes, etc.; (8) reduces risk of contamination of food products that would result from microbes, such as Salmonella, and their by-products, such as toxins, that settle on intermediate or finished food products; (9) reduces energy use by the processing equipment by increasing the retention time of heat (steam) in the preconditioner by restricting steam flow in the exhaust; (10) increases the quality of finished product by reducing variations in processing temperatures in the preconditioner; (11) has no moving parts or requirements for utilities (e.g., electricity, gas, plumbing) which reduces risk of system failure to machine design and risk in the production flow; and (12) is self-cleaning.
The subject matter disclosed herein improves upon or overcomes one or more of the shortcomings of solutions proposed for managing vent exhaust from food processing machines.